We have designed a case-control study to estimate the risk of uterine fibroids of >1.5 cm (as detected by a standard transabdominal and transvaginal ultrasound examination) in black women compared to nonblacks aged 35-49. Risk factors for the condition will be identified, and uterine tissue from women having fibroids removed will be studied to idenitify growth factors and genetic changes in the tissue that are associated with fibroid development. Data will be collected from 300-600 cases (both ultrasound identified and surgically identified cases of leiomyomas) and 300 controls (women found to have no evidence of leiomyomas at ultrasound) from the membership of a health care plan that serves approximately equal numbers of blacks and whites. A personal interview has been designed to provide information on demographic factors, medical history, dietary intake, reproductive history, life style factors, and occupational/environmental exposures. Blood will be collected (after fasting) in order to measure lipids, insulin, antibody titers for Chlamydia and Cytomegalovirus, endogenous gonadotropins, and potential susceptibility genes. Blood pressure, heart rate, weight, height, and waist-to-hip ratio will be measured. Medical record data will provide descriptive information on nonresponders. Tissue from surgical specimens will be analyzed for growth factors, genetic factors, and steroid receptor levels.